1. Field of the Invention
This disclosure relates to a method and system of securing floating platforms and other vessels. More specifically, the disclosure relates to a method and system for securing the floating platforms and other vessels with shared mooring lines.
2. Description of the Related Art
Deep-water offshore platforms, including Spars, are generally moored to the seabed through catenary mooring lines, such as chains and cables. These mooring lines are connected between the platforms on one end and structures on the seabed on the other end. The lengths can be significant and in many cases exceed one or more kilometers (or miles).
Movement of the offshore platform relative to the seabed is generally accommodated and factored into the weight, strength, length of the lines and seabed structures, and other parameters, so that under normal conditions, the system remains connected between the platform and seabed. However, there are sometimes unforeseen events that can cause an overload condition. It is known that an overload condition can break or otherwise destroy at least a portion of the connections, including the lines and anchors holding the lines to the seabed, at considerable expense.
When repairs are required to a connection, it is sometimes necessary to loosen the tension on the line to be able to cut or generally disassemble the connection, so that the repairs can be accomplished. However, due to the significant length and size of a typical mooring line, there is generally insufficient payout of line available to be able to adequately loosen the line.
One option is to specially attach additional line to the end of the existing mooring line to be able to payout the line farther. While in the abstract, such a remedy would seem natural, the size and length of the lines does not make this option particularly suitable. For example, a typical 60 feet of chain weighs about 2,500 kilograms and about 00 feet can be needed for one line for sufficient payout of line. Loading 12,500 kilograms of large size chain for each mooring line needing repair down into the depths of a floating platform that is in production with explosive hydrocarbons is risky at best.
Another option is to move the floating platform closer to the seabed connection to provide more payout of the line. However, movement in one direction presupposes that there is enough payout in the opposite direction, which is generally insufficient as discussed above. Further, the floating platform is generally connected to multiple production risers. A large movement of the platform can disrupt the connections and is generally not a satisfactory solution.
Therefore, there remains a need for a method and system for providing an increased payout of a mooring line without necessitating supplying additional quantities of lines to the existing lines on the floating platform.